Here's how to prepare for the questions you hope you never get.

The Internal Revenue Service's most intimidating weapon is the power to audit—and well-heeled taxpayers are more likely to be the target.

Audits are rare and getting rarer as the agency faces funding cuts. Fewer than 1% of taxpayers endured one last year, according to IRS figures. But while the audit rate has fallen over the past five years for taxpayers who earn less than $200,000, the rate has risen for those earning $200,000 to $1...